

#include <iostream>
#include <string>
#include <cstdio>
#include <string.h>
#include <errno.h>
#include <cstdlib>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

int main()
{
    pid_t id = fork();
    if(id < 0)
    {
        printf("errno : %d, errstring: %s\n", errno, strerror(errno));
        return errno;
    }
    else if(id == 0)
    {
        int cnt = 5;
        while(cnt)
        {
            printf("子进程运行中， pid: %d\n", getpid());
            cnt--; 
            sleep(1);

        }
       // int *p = nullptr;
       // *p = 100;
        exit(123);
    }
    else
    {
        
        int status = 0;
        pid_t rid = waitpid(id, &status, 0); 
        if(rid > 0)
        {
            //printf("rid:%d , status:%d\n exit signal:%d\n",rid,(status >> 8)&0xFF, status&0x7F);
            
            if(WIFEXITED(status))
            {
                printf("wait sub process success, rid: %d, status code: %d\n", rid, WEXITSTATUS(status)); 
            }
            else
            {
                printf("child process quit error!\n");
            }
        }
        else
        {
            perror("waitpid");
        }
        while(true)
        {
            printf("我是父进程: pid:%d\n", getpid());
            sleep(1);
        }
    }
}


 //  while(true)
 //  {
 //      int a = 1/0;
 //      printf("hello world\n");
 //      sleep(1);
 //  }

 // char *p = nullptr;
 // *p = 'a';
